Winter depression (Seasonal Affective Disorder, SAD) is a common disorder, affecting 4-10% of the population in northern latitudes. Although bright light therapy has been shown to be effective in treating SAD in studies lasting a week or two, controlled trials have not yet established its efficacy in longer trials. Dawn simulation, a gradually increasing illuminance occurring during the two hours before awakening, is a new potential treatment for SAD which is more convenient than the bright light box therapy. Greater convenience may lead to better compliance. In two pilot studies we found that dawn simulation improved the depression; in two controlled studies, we found that one week of dawn simulation is effective in treating SAD. Because of the translucence of the eyelids and the increased sensitivity of the retinae in the early morning hours, dawn simulation could work by mechanisms similar to those hypothesized for bright light therapy. The purpose of this study is to compare dawn simulation and bright light therapy in the treatment of SAD. In 7-week, parallel design, drug-free SAD (N= 120) subjects with no other major medical problems will be randomized to one of the two treatments conditions. Weekly depression ratings before and during the treatments,will be used to assess the relative efficacy of the light treatments. The study will provide important data concerning the efficacy of both dawn simulation and bright light treatment in winter depression.